1. Technical Field
The present invention relates to an emergency stop apparatus for an elevator, and more particularly to an emergency stop apparatus for an elevator having a simple structure as well as effectiveness, which may facilitate to reduce manufacturing and maintaining cost.
2. Description of the Prior Art
The elevator is generally designed to ascend and descend at a regular speed in an at least two-story building. However, the elevator car often descends much faster than a normal speed for reasons of malfunction of controller or other units, especially in downward motion. In order to prevent accidents by such factors, the elevator ordinarily includes an emergency stop apparatus.
U.S. Pat. No. 5,299,661 issued on Apr. 5, 1994 discloses an elevator system having a bidirectional overspeed control device and a governor rope circularly connected to sheaves mounted to upper and lower portions of a hoist way. According to the patent, the bidirectional overspeed control device includes a bidirectional governor, safety brakes and a bidirectional linkage apparatus, in which the bidirectional governor clutches the governor rope in the event of an overspeed condition, thereby operating the bidirectional linkage apparatus which connects the governor rope to the safety.
FIG. 1 shows the emergency stop apparatus employed in such elevator system schematically. Referring to the figure, the emergency stop apparatus of the conventional elevator system is installed to an elevator car 2 moving vertically along a guide rail 1 in a hoist way inside a building. The emergency stop apparatus includes a speed governing unit 10 installed to one side of the guide rail 1 for detecting speed of the elevator car 2 in order to brake the elevator car 2 when the car 2 moves faster than a certain speed, a transmission unit 20 connected to the governor 2 for transmitting power from the speed governing unit 10, and a brake 30 installed under the elevator car 2 for restraining the elevator car 2 by receiving power from the speed governing unit 10 through the transmission unit 20.
The speed governor 10 includes a governor 11, a driven pulley 12, and a governing loop 13. The governor 11 includes a rotating body 11A for rotating at the same speed as speed of the elevator car 2 and stopping when the elevator car 2 moves faster than a regular speed, and a centrifugal weight 11B having same rotary axis as the rotating body 11B. The driven pulley 12 is mounted at a lower end of the guide rail 1 and the governing loop 13 is wound through the rotating body 11A and the driven pulley 12.
The transmission unit 20 includes a connecting member 21 and a multi-joint link member 22. The connecting member 21 is combined to the governing loop 13 in order to lift at the same speed as the governing loop 13. The multi-joint link member 22 is combined to the connecting member 21 and activates a pair of wedges 31 of the brake 30 described below when the governing loop 13 comes to a halt.
The brake 30 is well shown in FIGS. 2 and 3. Referring to the figures, the brake 30 includes the wedges 31, an elastic ring 32, a wedge seat 33 and sliding rollers 34. When stopping the elevator car 2 in emergency, the wedges 31 are drawn by the link member 22 of the transmission unit 20 and then come in contact with the guide rail 1. As described above, the wedges 31 in contact with the guide rail 1 make frictional force to the guide rail 1, and at this time, the elastic ring 32 exerts vertical force to the wedges 31 in order to increase the frictional force between the wedges 31 and the guide rail 1. The wedge seat 33 is mounted between outer sides of the wedges 31 and an inner side of the elastic ring 32. The wedge seat 33 has is formed to become gradually narrower in its upward direction such that the wedges 31 may be pressed by more vertical force from the elastic ring 32 as the wedges 31 ascend. The sliding rollers 34 are located between the outer surface of the wedge seat 33 and the inner surface of the wedges 31 and play a role of eliminating friction between the wedges 31 and the wedge seat 33 such that the wedges 31 may ascend inside the wedge seat 33 more smoothly.
The emergency stop apparatus of the conventional elevator system as constructed above is operated as follows.
If the elevator car 2 moves in excess speed due to a breakdown or a falling in the hoist way, the governor 11 is activated by the rotating body 11A and the centrifugal weight 11B rotating at the same speed as speed of the elevator. The governor 11 acts for stopping the governing loop 13 moving along with the elevator car 2. If the governing loop 13 stops, the link member 22 of the transmission unit 20 is linked to draw the wedges 31 of the brake 30.
If the wedges 31 are drawn by the link member 22 as described above, the wedges 31 move upward inside the wedge seat 33 formed to become gradually narrower in its upward direction, and then receives strong press inward through the wedge seat 33 from the elastic ring 32. Therefore, an inner surface of each wedge 31 comes in contact with an outer surface of the guide rail 1, resulting that the elevator car 2 stops by frictional force generated in the contact surface.
However, such emergency stop apparatus of the conventional elevator system has a problem of low spatial utility rate because it needs separate space for installing the speed governing unit 10 having the governor 11, the driven pulley 12 and the governing loop 13 outside the guide rail 1. Furthermore, because a separate link member 22 should be linked for transferring action of the governor 11 to the wedges 31, it has high manufacturing cost, and it is difficult to fabricate, install and repair the link member 22.